The savings come mainly from reduction in support staff, maintenance costs, food service and transportation which allows schools to retain teachers and academic programs that would have to be dropped otherwise. In order to keep the students on schedule academically, each school day is extended by an hour or two, thus resulting in no net loss of instructional time.

There’s little reliable research on how the shortened week impacts academic performance, but the studies that are available point to there being no difference. Specifically, the analysis carried out by the Colorado Department of Education released earlier this year shows that students in districts with four- and five-day weeks perform similarly.

It is the parents who typically have the most difficulty adjusting, with most schools reporting negative parental reactions due mostly to increased child-care expenses for the fifth day. Many are also wondering if the cost savings achieved via the shortened week really justify a disruption in the children’s and parents’ lives.

The savings, though, are less than you might think. A 20 percent reduction in school days seldom nets more than 2.5 percent slashed from the overall budget,according to a national study by senior policy analyst Michael Griffith of the Denver-based Education Commission of the States.

The vast majority of school spending goes to educator pay and benefits. None of the districts surveyed reduced those because instructional staff was required to work the same number of hours across the school year. Despite relatively meager savings, percentage-wise, some districts jumped at the chance to avoid losing teaching positions.

These estimates echo the experience at the Salida school district which, after switching to a four-day schedule last year, saved about $150,000. This seems a paltry sum considering the total district budget tops $19 million. But according to Superintendent Darryl Webb, even such small savings were worth it; they allowed the district to preserve teaching positions they wanted to avoid cutting.

In addition, after one year into the three-year experiment with the new schedule, another unexpected benefit popped up: an uptick in test scores. Webb thinks that the increased “sense of urgency” of the shortened week seems to encourage teachers and students to make every hour in the classroom.

The four-day week has its critics too, especially in light of the fact that shortening the time students spend in school seems to go against the academic reform push for more instructional opportunities rather than fewer.

Critics of the four-day week, while acknowledging that even minimal savings can mean a lot to a district, see the practice as adding to an already troubling summer learning loss and flying in the face of trending reform efforts aimed at expanding instructional time.

“I know some smaller rural districts have been doing it a long while and they have strategies that seem to be working,” said Jennifer Davis, president and co-founder of the Boston-based National Center on Time and Learning. “But the policy decision, at a time when we’re trying to upgrade our education system in America, is in the wrong direction.”